Learn by Doing – State Hypotheses (Proportions)

In each of the following examples, a test for the population proportion (p) is called for. You are asked to select the right null and alternative hypotheses.

Scenario 1:The UCLA Internet Report (February 2003) estimated that roughly 8.7% of Internet users are extremely concerned about credit card fraud when buying online. Has that figure changed since? To test this, a random sample of 100 Internet users was chosen, and when interviewed, 10 said that they were extremely worried about credit card fraud when buying online. Let p be the proportion of all Internet users who are concerned about credit card fraud.

Scenario 2: The UCLA Internet Report (February 2003) estimated that a proportion of roughly .75 of online homes are still using dial-up access, but claimed that the use of dial-up is declining. Is that really the case? To examine this, a follow-up study was conducted a year later in which out of a random sample of 1,308 households that had Internet access, 804 were connecting using a dial-up modem. Let p be the proportion of all U.S. Internet-using households that have dial-up access.

Scenario 3: According to the UCLA Internet Report (February 2003) the use of the Internet at home is growing steadily and it is estimated that roughly 59.3% of households in the United States have Internet access at home. Has that trend continued since the report was released? To study this, a random sample of 1,200 households from a big metropolitan area was chosen for a more recent study, and it was found that 972 had an Internet connection. Let p be the proportion of U.S. households that have internet access.

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This material was adapted from the Carnegie Mellon University open learning statistics course available at http://oli.cmu.edu and is licensed under a Creative Commons License. Other materials used in this project are referenced when they appear.

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